ProjectSummary Itisnowwellacceptedthattumor-derivedmutantformsofp53arepotentlyoncogenic.Silencingmutant p53, or inducing the degradation of this protein, can markedly impair tumor growth in vitro and tumor progressioninvivo.Theabilityofmutantp53todrivetumorprogressionisfrequentlymediatedbyprotein- proteininteraction,andthisisoftenreferredtoasthe?gainoffunction?(GOF)activityofmutantp53.One of our gaps in knowledge has been the identification of key GOF activities of mutantp53. Another has been investigation intohow coding region SNPs (singlenucleotidepolymorphisms) inp53 influence the mutantp53GOF.OneoftheHolyGrailsofcancerbiologyhasbeentheidentificationofcompoundsthat canreactivatethep53pathwayintumorscontainingmutantp53,byrefoldingmutantformsofp53intowild type conformation and activity. Severalgroups have reported the identificationof compoundsthatact in these ways. Another key gap in our knowledge has been how coding region SNPs (single nucleotide polymorphisms)inp53impactthefoldingofmutantp53,andtheefficacyofcompoundsthatrefoldmutant p53. Inthisapplication,wetakeaimattwocodingregionSNPsinp53:Pro72ArgandTyr107His.Werecently publishedthatthecodon72variationisapotentintragenicmodifierofmutantp53GOF.Specifically,the Arg (R72) variantof mutantp53 is asuperior mediator oftumor cell invasiveness and isassociated with poor prognosis in women with breast cancer. We will delve intoan investigationof the influence of this SNP on mutant p53 GOF, usingnovel mouse models for the R175H mutation, containingeither P72 or R72.Wewilllearntheirimpactonp53structureusingNMR,andontheirinfluenceontheefficacyofp53- refolding compounds. This aim constitutes a structural, molecular and in vivo analysis of the codon 72 SNPofmutantp53. WehaveobtaineddatathattheY017Hvariantofp53altersthestructureandactivityofthisprotein.We will explore the effect of this African-specific SNP on p53 function in a novel mouse model. We have identified genes with impaired transactivationbyY107H, including thechromatin modifier PADI4;?we will exploreitsimpactonp53functionandtumorsuppression.Insum,forbothaimsweemployacombination ofgeneexpression,protein-proteininteraction,cytotoxicityandnovelmousemodels.Wehaverecruited expert collaborators like Donna George (Penn), John Karanicolas (Fox Chase Cancer Center) and Darren Carpizo (Rutgers-Cancer Institute of New Jersey). These Investigators bring to bear their complimentary expertise to address an important and clinically-relevant question: how can we better harnessp53toeradicatecancer.